FILE - In this Aug. 13, 2016 file photo, author Robert Caro attends the East Hampton Library's 12th Annual Authors Night Benefit in East Hampton, N.Y. The Pulitzer Prize-winning historian is planning an audio-only release, “On Power,” drawing upon his years as an investigative journalist and his research into the lives of President Lyndon Johnson and municipal builder Robert Moses. The book will be released through the audio producer Audible Inc., on May 9. (Photo by Scott Roth/Invision/AP, File)

NEW YORK (AP) — Robert Caro's next project is for ears only.

The Pulitzer Prize-winning historian is planning an audio-only release, "On Power," drawing upon his years as an investigative journalist and his research into the lives of President Lyndon Johnson and municipal builder Robert Moses. "On Power" will be narrated by Caro and released exclusively through the audiobook producer and distributor Audible Inc., which told The Associated Press on Monday that it had set a May 9 release date.

"My books are an attempt to examine and explain political power: how it is created, how it works, how it can be used — for good and for ill," Caro said in a statement provided to the AP. "I thought it was important to try to do that because that power shapes all our lives — in ways large and small. And I felt that the more America understands about political power, the better informed our voters would be, and then, hopefully, the better our democracy would be."

"Over and over again," he added, "I have come across aspects of political power that I had not previously understood, or, indeed, known existed. I agreed to do 'On Power' because I thought it might add something if I talked, in a more informal manner than in my books, about some moments that helped me personally in that learning process."

Caro, 81, is known for his biography of Moses, "The Power Broker," and for his epic series on Johnson, which he began more than 40 years ago. All five of his previous books have come out in audio editions, none narrated by Caro. (His books sometimes run more than 1,000 pages.) He is proudly old-fashioned in his working methods, preferring typewriters to computers, and "On Power" should prove a brief diversion from the fifth and presumed final volume about LBJ. No publication date has been set for the book, one of the most highly anticipated releases for a work of history. The previous four Johnson books have brought Caro a Pulitzer, a National Book Award and numerous other honors.

The audio narrative was initiated by Audible after senior director Tyler Cabot saw Caro speak last September at Harvard University during a celebration of the Pulitzer's centennial and contacted the historian. Caro, in a telephone interview Monday, said he liked the idea because he puts in extensive time on his speeches and has regretted that they didn't exist in a more permanent form. "On Power" is an adaptation of two of his public talks into a single, new narrative and will likely run under two hours, compared with more than 60 hours for the audio version of "The Power Broker."

"I've never done anything like this before," Caro said of the audio work. "And some of the stories I tell I've never told in public before."

According to Audible, an Amazon.com-owned company, "On Power" will provide Caro fans "a more personal introduction to his body of work and life" and a showcase for "his trademark wit and revelatory insight."

Audio sales have soared in recent years, although audio-only releases by authors of Caro's stature remain relatively uncommon. Previous audio-only works include Tom Wolfe's novella "Ambush at Fort Bragg" and Jeffrey Deaver's novel "The Starling Project."